1. Field of the Invention
The invention disclosed herein relates to data processing devices and more particularly relates to post processing devices for keyboards, character recognition machines, and speech analyzers.
2. Description of the Prior Art
A threshold problem in post processing of the output stream from a keyboard, character reader, or voice analyzer is presented by the necessity of executing a quick comparison of the output word with a dictionary of acceptable words and generating a go/no go signal indicating the presence or absence of a conventional word.
Attempts have been made in the prior art to formulate an efficient means for converting the information in an alpha word to a significant address for storage means so as to access information as to whether that output word was, in fact, correctly spelled. For example, J. J. Giangardello, in the IEEE Transactions on Engineering Writing and Speech, Vol. EWS-10, No. 2, December 1967, page 57, in an article entitled "Spelling Correction by Vector Representation Using a Digital Computer," discloses the use of vector representation of alpha words by assigning the numbers 1 through 26 to the letters "A" through "Z" respectively and calculating a vector magnitude and angle for accessing the word from a memory in a general purpose computer. This disclosure, suffers from a defect which is typical of the prior art, namely, that the conversion of the garbled word to be examined into a key address results in an ambiguous access. The vector address generated can randomly access an occupied or valid address for one or more dictionary words without any of the dictionary word corresponding to the intended word which was garbled into the word under examination. In other words, the representations are not unique for each valid dictionary word. What is needed in the art is an apparatus which generates address vectors for words under examination, which have no ambiguity, and yet maintain the size of the reference matrix within reasonable bounds.
A step toward this goal was made by A. M. Chaires, et al., in U.S. Pat. No. 3,925,761, entitled "Binary Reference Matrix for a Character Recognition Machine," issued Dec. 9, 1975 and assigned to the same assignee as the present application. Chaires, et al discloses a binary reference matrix wherein each letter in the alphabet is assigned a unique numeric value and a vector magnitude and angle is calculated for each dictionary word. The magnitude and angle form the x and y coordinates for the matrix with a binary 1 being stored in each position of the matrix representing a valid dictionary word and a binary 0 in those positions not representing a valid dictionary word. While the organization of the binary reference matrix minimizes the size of the array needed for accurate verification by choosing numerical values for the alphabetic characters in an inverse proportion to the characters' propensity for error, the representations for the dictionary words in the Binary Reference Matrix (BRM) are not unique and error events must be associated with a propensity to map a garbled word into a sparsely populated region of the matrix to minimize the likelihood of false verification due to round off error in the magnitude and angle BRM representations. This necessitates that a substantial number of blank storage locations be provided in order to create the sparsely populated region required.